A spokeswoman for the courts insists the courts are insect-free, but the claim came as attorneys for landlords and tenants said bed bug disputes are filling the docket in New York City courts. At stake are thousands of dollars, including the cost of extermination, destroyed property, and rent for infested apartments. The cases are also setting new precedents in the emerging field of beg-bug law.

"To be honest, up until a year ago, I never even heard of a bed bug or knew about them. I never came across it," a real estate attorney, Martin Heistein, said.

According to the Department of Housing Preservation and Development, which keeps track of complaints about bed bugs and issues violations against property owners who fail to exterminate them, there were 8,830 bed bug complaints in fiscal year 2008, which ended June 30, up from 1,839 in 2005. This year, the department issued 2,757 bed bug violations, up from 366 in 2005.

In New York City, landlords are responsible for getting rid of bed bugs in infested buildings and units and they must pay for extermination.

This was not always the case, but a turning point was a 2004 case, Ludlow Properties, LLC, vs. Young, in which Judge Cyril Bedford sided with a tenant who refused to pay rent for six months because of a persistent bed bug problem.

"Although bedbug are classified as vermin, they are unlike the more common situation of vermin such as mice and roaches, which, although offensive, do not have the effect on one's life as bedbugs do, feeding upon one's blood in hoards nightly turning what is supposed to be bed rest or sleep into a hellish experience," Judge Bedford wrote.

A lawyer at Shafer Glazer, LLP, Timothy Wenk, said the Bedford decision has rippled through the legal community. He said the case reversed a long-standing decision in a 1908 case, Jacobs v. Morand, which held that tenants must pay rent regardless of vermin infestation.

Now, Mr. Wenk said, "The tenants are winning the landlord-tenant cases." He pointed to another recent case, Mathias v. Accor Economy Lodging, Inc., in which a Chicago judge awarded $362,000 to a brother and sister who were bitten by bed bugs while staying at a motel. "The brother and sister really hit pay dirt and got pay dirt," said Mr. Wenk, who called it "the mother of all bed bug cases."

One reason why bed bug disputes are landing in court is because it is hard to prove where the bugs originated. While some landlords have accused their tenants of bringing bed bugs into the building, tenants have reported bed bug infestations that spread to their homes from neighboring apartments.

"It gets back to the issue of responsibility," an attorney for tenants, Ronald Languedoc, said. Mr. Languedoc, who is an associate at the firm Himmelstein McConnell Gribben Donoghue & Joseph, said he has heard of cases where landlords asserted claims against their tenants, but he said he could not imagine how to prove that was the case. "In law, the party that asserts a claim usually has a burden of proof," he said. "I think it is probably hard to track down where, precisely, they came from and how they got in there."

One attorney, Steven Wagner, said he is currently handling a case for a client on the Upper West Side who moved out of his new apartment within 60 days because of bed bugs. The client, who was renting a three-bedroom apartment on West 92nd Street for $7,000 a month, learned shortly after moving in that apartments on adjacent floors were infested with bed bugs. Mr. Wagner said his client's landlord assured him that there would be no problem, but then the client's son was bitten in the middle of the night.

"My client feels as if they had been defrauded into even signing this lease," Mr. Wagner said. "Had they known there were bed bugs in the building, they never would have signed the lease."

Mr. Wagner said bed bug cases were unlikely to yield huge rewards, but litigation is a way to minimize losses. "If people sign a one to two year lease at these kinds of rents, and then their children start getting bitten, they're angry," he said. "In these cases, people feel they have no choice."

He speculated that bed bug cases could have a ripple effect in the real estate market. "I wonder if this is a new way of getting rid of tenants who are regulated," he said.

He also predicted new case law would emerge from a growing area of litigation. "I don't know how bad the bed bug epidemic is, but I can tell you it is non-discriminatory," he said. "There are going to be people who are spending a lot of money and can litigate these issues."